Method of making lead arsenate.



L. SHEPHERD.

METHOD OF MAKING LEAD ARSENATE. APPLICATION FILED OCT-14,1911.

H 1,175,565., Patented Mar. 14,1916.

WlTNESSE5- INVENT R- w?amm 0.

ATTORNEY- tions in this process have LEE SHEPHERD, OE CLEVELAND, OHIO,ASSIGNOR T0 THE'HARSHAW, FULLER & GOODWIN COMPANY, OF CLEVELAND, OHIO, ACORPORATION OF OHIO.

mnrnon or Max ne LEAD ARSENATE Specification of Letters Patent.

Patented Mar. 14, 1916.

Application filed October 14, 1911. Serial No. 654,626.

To all whom itmay concern:

Be it known that I, LEE SHEPHERD, a citizen of the United States, and aresident :of Cleveland, county of Cuyahoga, and State of Ohio, haveinvented a new and useful Improvement in Methods of MakingLead Arsenate,of which the following is a specification, the principle of theinvention being herein explained and the best mode in which I havecontemplated applying that principle, so as to distinguish it from otherinventions.

- The ordinary method of manufacturing lead arsenate has been by aso-called wet process, wherein, for example, a soluble arsenate iscaused to react with a suitable lead compound so as to precipitate therelatively insoluble lead arsenate. Various modificaarisen dependingupon the character of the salts used, but all are alike objectionable inthat solutions more or less dilute in character have to be dealt with,and that the lead arsenate, when finally formed, must be separated orfiltered out of a solution with attendant delay. I am aware that it hasbeen attempted to avoid the objectionable features of such wet processesby roasting combining weights of white arsenic and a suitable leadcompound in the presence of oxygen so as to produce the lead arsenate ata single operation. A number of dilficulties, however, likewise attendthis method of treatment, especially if a relatively pure arsenate isdesired, and this is more or less essential, at least so far as anyadmixture of arsenic in the resulting product is concerned.

The object of the present invention, accordingly, is the production ofsuch arsenate by directly 'combining'white arsemc with a suitable leadcompound in such away as to insure the reaction being a complete one, as

also' to permitthe proper proportions of the entering materials to bereadily maintained at all times. v

To the accomplishment of the foregoing and related ends, .the invention,then, consists of the steps hereinafter described and particularlypointed out in the claims.

The annexed drawing andthe following description set forth in detailvarious approved, methods of carrying out the invention, such disclosedmodes, however, cons tube of the blow pipe,

stituting but several of the ways in which the principle of theinvention may be used.

In said annexed drawing :-Figure 1 represents diagrammatically avertical section of a suitable apparatus for carrying on the presentimproved process; and Fig. 2 is a plan view, partly in section of amodification in construction.

My improved process is a continuous one and may be briefly described asconsisting in burning ingas, under proper conditions, a, suitablemixture of either metallic lead or a lead compound, along with whitearsenic. Preferably lead sulfid, which is obtainable in practically pureform as the ordinary galena ore concentrate, is employed, not onlybecause it is obviously cheaper than the metal, which has to be smeltedfrom such. ore, but also because the sulfur constituent, beingcombustible, will actually contributeto the maintenance of thetemperature required for the reaction between the lead and the arsenic.The latter is the ordinary white arsenic of commerce. While it ispreferred to use natural gas for burning the lead and arsenic, onaccount of its cheapness and heat value, other gases can of course beused.

The white arsenic in commercial form is, of course, already a finepowder, and in order to prepare the lead sulfid ore for use in thepresent process, it likewise is ground exceedingly fine, such grindingbeing best done by the air flotation method, which does not require tobe described in detail. The ground ore and white arsenic are thenintimately mixed in the proper proportion, such In order to eifect'thecombustion of the two ingredientsjust described, the mixture formedthereof is charged into a feeding hopper 1 (Fig. 1), provided with ascrew 2 or other feed device, by means of which it may be continuouslyfed into the air et 3 of a blow pipe. Air is forced through such jet bya blower 4, while a p1pe'5 surrounding the jet so as to form the outeris connected with I White arsenic. The products of the combustion arepro ecte'd into a combustion chamber 7. which may consist of anymaterial not affected by the intense heat or attacked by the products ofthe combustion. Thus it may be constructed of iron or suitable brick,but if of the latter, the brick must not contain silica or othercompound capable of entering into combination with the lead, so as to befused. Magnesite or chrome brick are suitable materials for thispurpose. A. hopper or receptacle opens into the fioorof chamber 7, inorder to receive any incombustible earthy materials which may bemingledwith the lead sulfid ore. Coextensive with'the combustionchamber, as it has been'termed, is an extension or flue 9, which isshown as being constructed of brick (brick of the kind just describedbeing of course used for this purpose), although it may be of iron, asthe combustion chamber proper; or both combustion chamber, and thisextension, or continuation thereof, maybe of brickin the form of asingle compartment 10, as shown in Fig. 2. External heat. may be appliedto this extension of the chamber, as by burners 11, in order toinitially raise the same to the proper temperature, or to assist inmaintainmg such temperature, if it is not desirable to lntroduce enoughgas in the Initial combustion step to heat the entire compartment."

'result presently to be set forth.

Connected with the furnace, as I shall 1 term the complete combustionchamber, with its extension, is a cooling pipe 12,-preferably of metaland of such length and so constructed to cool the fumes resulting fromthe combustion in the former sufliciently to enable them to be passedthrough one or morev separators or dust collectors 13 in which any solidproduct may be deposited. A final separation of such product isefiiected by means of bag filters 14 of-well I known construction.

The circulation of air through the apparatus is accomplished by means ofa fan 15 placed at a suitable point in such apparatus, being shown aslocated after the bag filters last referred to. The exhaust gases fromHe filters, whether 'forced or sucked therethrough are preferablydischarged into a-stack 16.

The products of the combustion occurring at the entrance to the furnaceare probably in ,the state of .vapors and may be con,-

'--'*'si'de'redas consisti ng of lead arsenate and ll-j had arsenite, asle d. xithfll'fifimiqlls oxid (AS203) and arsenic oxid (AS205), thesulfur in the ore being of course, converted into sulfur dioxid (S0which is a gas. A high temperature, approximating that at which thiscombustion takes place, is maintained long enough for these "apors, orproducts of combustion whatever their character, to'completely react,the result of such reaction, disregarding the sulfur dioxid, being leadarsenate, where the lead sulfid and White arsenic are mixed together inthe proper proportions, and sufficient air is admixed with the gas.-This lead arsenate settles in the cooling pipe, the dust collectors andthe filter bags, from which'it may be removed at'intervals. It is anextremely finely divided White powder, very light in gravity and can beused in this condition or be mixed with water to form a paste, if moreconveniently handled in the latter form. The term lead arsenate as hereused, is of course intended to designate the commercial product and notany one specific lead arsenate, commercial lead arsenate usuallyconsisting of. a mixture of two chemically difi erent lead arsenates asis Well known.

It has already "been indicated that in place of lead sulfid, metalliclead or any suitable compound of the metal such as the oxid, carbonate,or'basic carbonate may be used, although the advantage in employing thesulfid over any of these should be obvious. The process in hand is alsoapplicable to the making of other metallic arsenates than lead arsenate,such for example as iron arsenate and copper arsenate. Where an oxid, oroxygen yielding com-pound is employed, the oxidizing of the arsenic isassisted, and instead of depending upon the oxygen from the air or thelead compound for this purpose, some oxidizing material such as nitermay be introduced along with the lead and arsenic mixture. The process,likewise is not limited to use of the specific compound of arsenic,viz., white arsenic, that is named; but the higher oxid can be employedif found commercially expedient.

The combustion step, furthermore, may be assisted by heating the airwhich is introduced through the burner.

In conclusion it may be remarked that it is quite possible, instead ofintermixing then introduce them into a heated chamber or furnace. Thisin fact is the arrangement illustrated in Fig. 2, where two hoppers 1and associated burners 17 are arranged to discharge into the furnace 10.The feeding that prerieas ydescr bes. n gard regards the process to theterms burning and combustion, as herein used, it should be explainedthat the exact character of the phenomena attending the ignition of theintermingled streams of gas and air discharged from the burner, alongwith the powdered lead and arsenic borne by such gas and air, isdiliicult to ascertain. These terms are hence not to be understood asbeing necessarily employed in a strictly literal sense, but to includeeither an actual oxidation of any of the ingredients or their simplevaporization. i

Other modes of applying the principle of my invention may be employedinstead of the one explained, change being made as herein disclosed,provided the step or steps stated by any one of the following claims orthe equivalent of such stated step or steps be employed.

I therefore particularly point out and distinctly claim as myinvention 1. The method of making lead arsenate, which consists inburning together a combining. mixture of a lead compound and an arseniccompound in the presence of air, whereby the products of theircombustion v are. intermingled; and then cooling such products. a

2. The method of making lead arsenate, which consists in burningtogether a combining mixture of a lead compound and white arsenic in thepresence of air; whereby the products of their combustion areintermingled; and then cooling such products.

3. The method of making lead arsenate, which consists in burningtogether a combining mixture of lead sulfid and white arsenic, both infinely divided state, in the presence of air; and then cooling suchproducts.

4. The method of making lead arsenate, which consists in discharging anignited combustible mixture of a lead compound, an arsenic compound anda hydro-carbon fuel into a highly heated chamber; and then cooling theproducts of the resulting combustion.

5. The method of making lead arsenate, which consists in discharglng anignited combustible mixture, consisting of a suitable lead compound,white arsenic and hydro-carbon fuel, into a highly heated chamber; andthen cooling resulting combustion.

6. The method of making lead arsenate, which consists in discharging anignited combustible mixture, consisting of lead sulfid and whitearsenic, both in a finely divided state together with a hydro-carbonfuel, into a highly heated chamber; and then cooling the products of theresulting combustion. I

7. The'method of making lead arsenate, which consists in discharging anignited combustible mixture, consisting of lead sulfid and whitearsenic, both in a finely divided state, together with natural gas, intoa highly heated chamber; and then cooling the products of the resultingcombination.

Signed by me this 12th day of October,

LEE SHEPHERD. Attested by- ANNA L. GILL, JNo. F. OBERLIN.

the products of the

